11-01-2018 8:12 PM
I have the Royal Mail measurements in front of me and the size for a large letter is 25mm thickness, 353 x 250mm and max weight 750g.
My postmaster assures me that they are allowed to 'gently' pull the items through the cut out slot guides, however, the slightest resistance , then they have top charge for the next size, and that would indeed be, the small parcel size.